The present invention relates generally to “smart” cards and, more particularly, relates to a smart card which has at least one metal layer and is capable of radio frequency (RF) transmission.
A “smart” card is a card that includes an embedded electronic chip which contains memory and/or a microprocessor and associated electronic circuitry that stores and transacts data. The card data is transacted via a card reader that is part of a computing system.
Smartcards may be of three general types: (a) “contactless”, (b) “contact”, and (c) “dual interface.” A contactless smartcard includes an antenna by means of which RF signals are coupled between the smart card's electronic chip and an antenna of a card reader. That is, there is no direct electrical connection or contact between the card and the card reader. A contact type smart card has contacts which enable a direct electrical connection to be made between an electric chip on the card and a card reader. A dual interface smartcard has the antennas and the direct electrical contacts of the contactless and contact smart cards, so that it may operate as either a contactless or a contact smart card.
Typically, contactless and dual interface smart cards do not have an internal power source. Instead, their card antenna captures some of the RF interrogation signals emanating from the card reader, which the chip rectifies to power the card's electronics.
Contactless smart cards are becoming increasingly popular and are now finding wide use, including: in payment and ticketing applications, such as mass transit and motorway tolls; in personal identification and entitlement schemes on regional, national, and international levels; in citizen cards; in drivers' licenses; in patient card schemes; and in biometric passports to enhance security for international travel.
It has become very desirable and fashionable to make cards with one or more metal layers. A metal layer provides a decorative pattern and/or reflective surface enhancing the card's appearance and aesthetic value. This is especially desirable for use by high-end customers. However, a problem arises when using a metal layer with a contactless smart card, in that the metal layer interferes with radio-frequency (RF) communication signals between the card and the reader, and it could render the contactless smart card useless.
As shown in FIG. 1, prior art contactless smart cards with metal layers have used a layer 16 of ferrite material between a metal layer 12 and the internal antenna 22 of the card to shield the antenna from the deleterious effect of the metal layer. However, the ferrite layer tends to be relatively heavy, making the smart card too heavy, and the ferrite material is quite expensive. It is therefore desirable to provide a contactless smart card having a metal layer, in which card the amount of ferrite material is substantially reduced. Note: For purpose of showing a broader use of the smart cards of the invention, FIG. 1 and other figures show the cards to include a module 20 with a contact pad 20c to provide dual interface capability (i.e., contactless as well as contact operation). However, it should be understood that the problem with the ferrite layer is due primarily to the contactless (RF) operation.
It is therefore an object of the present invention to reduce substantially the amount of ferrite material utilized in a smart card with a metal layer. This is the case whether the smart card is designed to have contactless or dual interface capability.